Exhaust gas discharged from a diesel engine includes particle matter represented by soot and the like and nitrogen oxide represented by nitrogen monoxide and the like. As a means for removing the particle matter, a particle matter filter device which filters the exhaust gas with a filter carrier is known. As a means for removing the nitrogen oxide, a nitrogen oxide reductor is known as what reduces the nitrogen oxide with a reduction catalytic carrier after supplying urea water to the exhaust gas.
In the case that the particle matter filter device and the nitrogen oxide reductor are employed as an exhaust purification apparatus so as to purify the exhaust gas discharged from the diesel engine, firstly, the particle matter in the exhaust gas is removed by the particle matter filter device, and then the nitrogen oxide is reduced by the nitrogen oxide reductor. When these devices are arranged straight in an exhaust path, the path imperatively becomes long. Accordingly, there is a construction that the devices are arranged in parallel to each other and constructed integrally (for example, see the Patent Literatures 1 and 2).
However, when the particle matter filter device and the nitrogen oxide reductor are arranged in parallel to each other, it is difficult to secure the mixing time from the supply of urea water to the exhaust gas until the urea water and the exhaust gas are mixed uniformly. It is also difficult to introduce the exhaust gas including the urea water into the reduction catalytic carrier constituting the nitrogen oxide reductor uniformly without any bias. Accordingly, a perforated plate or the like must be arranged in the exhaust path, whereby construction of an exhaust purification apparatus must be complex.
It is necessary to control the supply amount of urea water corresponding to the discharge amount of exhaust gas from the diesel engine. However, it is difficult to mix the suitable amount of urea water exhaust gas and introduce them into the nitrogen oxide reductor.    Patent Literature 1: the Japanese Patent Laid Open Gazette 2005-155404    Patent Literature 2: the Japanese Patent Laid Open Gazette 2008-138654